> ## Documentation Index
> Fetch the complete documentation index at: https://docs.retellai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Prompt Engineering Guide

> Best practices for writing effective prompts that create reliable and natural-sounding AI phone agents

## Introduction

Prompt engineering is the foundation of creating effective AI phone agents. A well-crafted prompt determines how your agent interprets situations, responds to users, and handles edge cases. This guide provides proven strategies for writing prompts that agents can follow reliably.

<Note>
  This guide focuses on general prompt engineering principles. For agent-specific implementation:

  * **Single/Multi Prompt Agents**: Apply these principles directly in your prompts
  * **Conversation Flow Agents**: Use these principles within individual node instructions
</Note>

## Getting Started

To see examples of effective prompts, create a new agent in the Dashboard and explore our pre-built templates. These templates demonstrate best practices for various use cases.

## Best Practice 1: Use Sectional Prompts

Break large prompts into focused sections for better organization and LLM comprehension. This structured approach offers several benefits:

* **Reusability**: Sections can be adapted across different agents
* **Maintainability**: Easy to update specific behaviors without affecting others
* **Clarity**: LLMs process structured information more accurately

### Recommended Prompt Structure

```markdown theme={null}
## Identity
You are a friendly AI assistant for [Company Name].
Your role is to [specific purpose].
You have expertise in [relevant domains].

## Style Guardrails
Be concise: Keep responses under 2 sentences unless explaining complex topics.
Be conversational: Use natural language, contractions, and acknowledge what the caller says.
Be empathetic: Show understanding for the caller's situation.

## Response Guidelines
Return dates in spoken form: Say "January fifteenth" not "1/15".
Ask one question at a time: Avoid overwhelming the caller with multiple questions.
Confirm understanding: Paraphrase important information back to the caller.

## Task Instructions
[Specific steps the agent should follow]

## Objection Handling
If the caller says they're not interested: "I understand. Is there anything specific..."
If the caller is frustrated: "I hear your frustration, let me help resolve this..."
```

## Best Practice 2: Use Conversation Flow for Complex Tasks

When your agent needs to handle complex logic or multiple tools, consider using Conversation Flow agents instead of trying to manage everything in a single prompt.

### When to Switch to Conversation Flow:

* **Multiple decision branches**: More than 3-4 conditional paths
* **Tool coordination**: Using 5+ different functions/tools
* **State management**: Tracking multiple variables throughout the conversation
* **Reliability concerns**: Single prompt shows inconsistent behavior

### Benefits of Conversation Flow:

* Each node focuses on one specific task
* Deterministic tool calling and transitions
* Easier to debug and optimize individual steps
* More predictable agent behavior

## Best Practice 3: Explicit Tool Calling Instructions

<Note>This section applies only to Single/Multi Prompt Agents. Conversation Flow Agents handle function calls deterministically through their node configuration.</Note>

### The Challenge

LLMs often struggle to determine when to call tools based solely on tool descriptions. Without explicit instructions, agents may:

* Call tools at inappropriate times
* Fail to call tools when needed
* Use the wrong tool for a situation

### Solution: Define Clear Triggers

Always specify exact conditions for tool usage in your prompts. Reference tools by their exact names.

#### Example: Customer Service Agent

```markdown theme={null}
## Tool Usage Instructions

1. Gather initial information about the customer's issue.

2. Determine the type of request:
   - If customer mentions "refund" or "money back":
     → Call function `transfer_to_support` immediately
   - If customer needs order status:
     → Call function `check_order_status` with order_id
   - If customer wants to change their order:
     → First call `check_order_status`
     → Then transition to modification_state

3. After retrieving information:
   - Always summarize what you found
   - Ask if they need additional help
   - If yes, determine next appropriate action
```

### Best Practices for Tool Instructions

1. **Use trigger words**: List specific words/phrases that should trigger tool calls
2. **Define sequences**: Specify when tools should be called in order
3. **Set boundaries**: Clarify when NOT to call certain tools
4. **Provide context**: Explain why each tool is being called